Sara Errani, of Italy, winds up to return a shot to Flavia Pennetta, of Italy, during the second round of the 2013 U.S. Open tennis tournament Thursday in New York.

NEW YORK — A year ago, Flavia Pennetta was home nursing a wrist injury when her countrywomen Sara Errani and Roberta Vinci caused a stir in Italian tennis by playing each other in the quarterfinals of the U.S. Open. It was a collision of friendship and national pride wrapped into an emotional tennis match between doubles partners, which Errani won with relative ease.

This year’s Italian connection came Thursday afternoon, but with less fanfare. Pennetta took one side of the net in her comeback season at age 31, and Errani, seeded No. 4, was on the other. It produced the biggest upset so far in the tournament, with Pennetta pounding Errani’s weak serve and shots for a 6-3, 6-1 victory that took 1 hour 11 minutes in Arthur Ashe Stadium.

“It was perfect today,” Pennetta said after her match. “I am really, really happy. For me, this tournament is my favorite, so I am very happy to be here.”

That joy flowed right into the next match, in which Serena Williams made similarly quick work of her second-round opponent, Galina Voskoboeva of Kazakhstan. That 6-3, 6-0 rout took 1 hour 9 minutes, although it did come a day later than scheduled as rain pushed it back from Wednesday. It cleared the Ashe Stadium court quickly for the next featured match: Roger Federer’s second-rounder against Carlos Berlocq of Argentina.

Williams, the No. 1 seed, was happy to vacate the premises quickly.

“I think Galina played really well, especially in the first set,” she said. “She was hitting winners all over the place. You can tell she has improved a lot. Over all though, I think I did pretty well. I’m going to have to think about what I can do better.”

For Pennetta, who missed much of 2012 with the wrist injury, a quick trip through the second round was not a forgone conclusion. The injury sent her plummeting in the rankings, from her high of No. 10 to No. 166, as recently as Wimbledon. Now ranked No. 83, Pennetta remains the grande dame of this group of Italian players, having paved the way for Errani and Vinci to follow her up the rankings.

Errani, 29, has reached her highest ranking this year, but her results have tailed off. After reaching the semifinals of the French Open, where she was routed by Serena Williams, she fell in the first round of Wimbledon. Her hardcourts season has been dismal. She lost in the second round a few weeks ago in Mason, Ohio, to Vinci and in the first round in New Haven, Conn.

Errani said she was struggling with the pressure that comes with her new perch among the world’s best players.

“I feel that I am not fighting good because of too much pressure,” she said. “Because I don’t want to go on the court. I don’t want to play. I don’t want to stay there on the court. I feel very bad. So that is the problem for me. I have to find the way to find the motivation to go there.”

Two unseeded players made the Grandstand Court the place to be for a few hours in the afternoon, as Christina McHale, of northern New Jersey, needed three sets to get past Elina Svitolina of Ukraine, 6-4, 3-6, 7-5. McHale, 21, had a 3-1 lead in the second set before losing her grip on the match for a bit.

“I had to regroup after that second set and told myself to keep fighting,” McHale said. “I definitely thought my consistency really helped me today. When I needed to, I went for my shots a bit more.”